The fields of remanufacturing and salvaging machine components have greatly expanded in recent years. Many machine parts which in the past would have been scrapped are now returned to service. Giving machine components further service life not only conserves resources, but also can create new revenue sources for manufacturers, machinists and mechanics. One goal in remanufacturing many parts is returning them to original specifications. In other words, it is typically desirable to remanufacture a part such that tolerances, operation, reliability, etc. are as close as practicable to those of a new part. In some instances, remanufactured parts may even be superior to new parts, as inspection and testing of individual remanufactured parts can often be more rigorous than conventional analysis of many mass-produced new parts.
Remanufacturing parts used in certain hydraulic systems, such as fuel injectors, has a unique set of challenges. Many modern hydraulic systems utilize rapidly moving valve components to control the timing, rate and other characteristics of fluid flow. It is common in fuel injector systems to use a relatively small, rapidly moving valve to control the position or action of another component of the system, such as a plunger or admission valve. Over the course of a fuel injector's service life, its valve components may be required to actuate millions or even billions of times. The physical demands placed on such components will be readily apparent. When a fuel injector is to be remanufactured, certain functional surfaces of components of the fuel injector can be worn or otherwise damaged to the point that injector performance is compromised. Even seemingly miniscule deviations from specifications for critical components can have a relatively large effect on performance. Thus, returning certain fuel injector parts to specifications can be of paramount importance to successfully preparing a fuel injector for returning to service.
One set of fuel injector features whose dimensions, location, shape and orientation need to be relatively tightly controlled are valve seats. Over time, a valve member striking a valve seat can deform the valve seat. Fluid flowing at relatively high pressure and experiencing relatively rapid pressure changes can erode the valve seat and/or cause cavitation. U.S. Pat. No. 6,339,887 B1 to Straub et al. (“Straub”) proposes one strategy for refurbishing a valve seat in a fuel injector assembly. In Straub, a tool is moved along a known reference axis to lap the valve seat. The workpiece having the subject valve seat is purportedly aligned with the known reference axis to locate the tool. Aligning of the workpiece is achieved by locating part of the tool apparatus in a bore in the workpiece. While Straub's approach might provide successful valve seat refurbishing in some instances, or for certain valve types, positioning of the tool by locating in the bore has its drawbacks. On the one hand, the bore may be improperly aligned due to tolerances in original manufacturing. Thus, the supposed alignment between the tool and known reference axis may be unreliable. On the other hand, locating within a bore can be difficult, particularly for certain valve types.